This invention relates generally to a method and apparatus for setting the clearance for bearings. More particularly, the present invention relates to a method and apparatus for setting the clearance on roller bearings on comminution apparatus.
Ideally, there should be sufficient friction between the rollers and raceways to ensure that the rollers roll, not skid, as the shaft turns. In addition, contact should be maintained in and out of the load zone. The load zone is defined by the zone in which the rollers support the weight of the shaft. If there is too much contact, the bearing is preloaded and generates waste heat. If there is too little contact, the rollers roll in the load zone and skid when out of the load zone. Friction between the rollers and raceway during skidding generates waste heat. The rollers also tend to skew coming out of the load zone, causing undue cage wear.
There are several current methods of controlling internal bearing clearance. A first method utilizes a bearing with large internal clearances. The interference between the shaft and bearing bore is used to reduce the clearance to an acceptable level. The tolerance between the bearing and shaft must be compatible for this method to work.
A second method utilizes a tapered shaft sleeve to remove the excess clearance from the bearing. The bearing clearance is reduced by tightening a nut against the bearing, pushing it up the tapered sleeve until an arbitrary cold clearance value is achieved. The clearance is measured by inserting a feeler gage between the roller and raceway on the unloaded side. This method requires a good mechanic who utilizes trial and error.
Both of the above methods assume the chosen cold clearance is correct. In actuality, if a machine uses two identical roller bearings where the first is lightly loaded and the second is heavily loaded, the two bearings would require different internal clearances to operate properly.